This invention relates to an improved method for rearranging diisopropylbenzene dihydroperoxides to dihydric phenols such as hydroquinone and resorcinol whereby an emulsion is eliminated in the subsequent steps of separating and recovering the dihydric phenol from the complex reaction product.
It is known to oxidize dialkylbenzenes to the corresponding dialkylbenzene dihydroperoxide, and to rearrange the dihydroperoxide to the corresponding dihydric phenol. See for example Tanaka, et al U.S. Pat. No. 4,049,723, incorporated herein by reference for all purposes, the references disclosed therein, and the paper by J. Ewers, H. W. Voges and G. Maleck entitled "Process for the Production of Hydroquinone", Erdoel Kohle Erdgas, Petrochem. Br. Chem., Vol. 28, No. 1, 1975, pp. 34+. For example, the rearrangement of para-diisopropylbenzene dihydroperoxide to hydroquinone is accomplished by the acid-cleavage, in a ketone solvent such as methyl isobutyl ketone, of the para-diisopropylbenzene dihydroperoxide with an acid catalyst (Hoch splitting). Prior to rearrangement, the para-diisopropylbenzene dihydroperoxide is present in a complex mixture of by-products of the oxidation of the para-diisopropylbenzene. The hydroquinone must be subsequently recovered from such by-products and the ketone solvent present during the rearrangement.
As discussed in Tanaka, et al U.S. Pat. No. 4,049,723, various methods have been proposed for separating the hydroquinone from the by-products and ketone solvent. Invariably, in those processes wherein water is present, an emulsion is formed which makes the separation extremely difficult, time consuming and expensive. The process disclosed by Tanaka, et al eliminates the use of water during the separation step but has the disadvantage of adding large quantities of an aromatic hydrocarbon to the hydroquinone containing rearrangement product. The aromatic hydrocarbon must itself be subsequently recovered which presents further processing problems.